Hello everyone,
We have received a quote for a photovoltaic system on the roof of our single-family house planned for next year.
Our plan is to fully cover the south-facing roof.
The house measures approximately 9 x 12 m (30 x 40 feet) with the roof ridge running along the longer side, featuring a gable roof with a 45-degree pitch. There will be no roof overhang and one dormer.
You can find a floor plan of the attic with the basic dimensions attached. The photovoltaic system will be installed on the roof shown in the floor plan with the single dormer, not on the side with the two dormers.
What surprises us about the quote is that the supplier calculates a photovoltaic area of 45.8 sqm (493 sq ft), or 28 modules (just to be clear, photovoltaic area, not roof area), which results in a system size of 8.8 kWp according to the offer.
I won’t say what I calculated for the roof area myself (I’m really bad at math, but there are online calculators for that), but it seems to us that the system could be much larger based on the roof size. The original goal was to fully utilize at least 10 kWp or more. Does the dormer really take up that much space?
Additionally, our architect mentioned that there may be regulations regarding minimum distances to the roof edge and the dormer or something similar — is that possible?
Are we making a fundamental (calculation) error here, or is the system much too small given the roof size?
It would be great if you could share your assessment.
As an additional optional question, the system is proposed with IBC modules and an SMA inverter for a total net price of about 11,500 € (approx. 11.5K euros).
Are these components any good, and is that a reasonable price in NRW?
Best regards,
Tarnari
We have received a quote for a photovoltaic system on the roof of our single-family house planned for next year.
Our plan is to fully cover the south-facing roof.
The house measures approximately 9 x 12 m (30 x 40 feet) with the roof ridge running along the longer side, featuring a gable roof with a 45-degree pitch. There will be no roof overhang and one dormer.
You can find a floor plan of the attic with the basic dimensions attached. The photovoltaic system will be installed on the roof shown in the floor plan with the single dormer, not on the side with the two dormers.
What surprises us about the quote is that the supplier calculates a photovoltaic area of 45.8 sqm (493 sq ft), or 28 modules (just to be clear, photovoltaic area, not roof area), which results in a system size of 8.8 kWp according to the offer.
I won’t say what I calculated for the roof area myself (I’m really bad at math, but there are online calculators for that), but it seems to us that the system could be much larger based on the roof size. The original goal was to fully utilize at least 10 kWp or more. Does the dormer really take up that much space?
Additionally, our architect mentioned that there may be regulations regarding minimum distances to the roof edge and the dormer or something similar — is that possible?
Are we making a fundamental (calculation) error here, or is the system much too small given the roof size?
It would be great if you could share your assessment.
As an additional optional question, the system is proposed with IBC modules and an SMA inverter for a total net price of about 11,500 € (approx. 11.5K euros).
Are these components any good, and is that a reasonable price in NRW?
Best regards,
Tarnari
H
hampshire12 Nov 2019 23:50When optimizing for returns, you really don’t need to consider solar roof tiles.
Considering the many very different photovoltaic systems and materials used, this is a generalized statement about solar roof tiles and should not be taken seriously in terms of content.
Tego12 schrieb:
I am also a fan of good aesthetics, but my environmental conscience ultimately prevailed.
Considering the many very different photovoltaic systems and materials used, this is a generalized statement about solar roof tiles and should not be taken seriously in terms of content.
B
boxandroof13 Nov 2019 03:57Tarnari schrieb:
I would ask you the same: how can I calculate from which kWp the Renewable Energy Act surcharge becomes cost-effective? Approximately from 13 kWp
Regarding the area: take some photos, measure the roof (if needed, measure and count the tiles) and upload that on this other page. Try to plan the layout of the roof yourself on paper. A standard module is 1 x 1.7 meters (3.3 x 5.6 feet).
Only when you know the number of modules, the exact layout, and the options for stringing/inverter would I proceed with this or another solar installer.
Tarnari schrieb:
Following your advice, I will definitely ask the photovoltaic forum for guidance as well. However, since I feel very well supported and advised here, I would also like to ask: how can I calculate from which kWp the Renewable Energy Sources Act surcharge becomes worthwhile? As silly as it sounds, I am really bad at math and therefore unsure how and with which variables to set up the calculation.... Basically, you need to compare the additional costs from the still payable Renewable Energy Sources Act surcharge with the extra income:
Your self-consumption will typically be around 1000 kWh/year. On that, you pay, if I remember correctly, about €0.05/kWh (around $0.05/kWh), so roughly €50/year ($50/year). Per kWp, you make about €30 to €40 ($30 to $40) profit per year after depreciation. To come out ahead overall, you should therefore install at least 11.5 kWp, preferably the often recommended 13 kWp to be on the safe side.
Of course, the numbers can vary individually, but I hope this explains the approach to the calculation.
hampshire schrieb:
If you are optimizing for return on investment, you really don’t need to consider solar roof tiles.
Considering the many very different photovoltaic systems and materials used, that is a generalized statement about solar roof tiles and should obviously not be taken seriously. Solar roof tiles have a niche presence for good reasons… not just due to economic factors. You can read about all the details here in the forum.
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